AB1244 TOTAL KNEE ARTHROPLASTY IN PATIENTS UNDER 21 YEARS OF AGE: A U.S. NATIONWIDE ANALYSIS
Authors: J. A. Gibbons, C. Kahlenberg, D. Jannat-Khah, S. Goodman, P. Sculco, M. Figgie, B. Mehta
Journal: Annals of the Rheumatic Diseases (2022)

Background Total knee arthroplasty (TKA) is a procedure rarely performed in patients under 21 years old. However, the number of patients &lt;21 undergoing TKA in the United States (US) is unknown. In one of the largest US studies of an institutional arthroplasty registry, only 19 TKAs were performed in patients &lt;21 out of ~30,000 primary TKAs over 34 years 1 . While a few national or multi-national studies have been performed outside the US, these studies have small cohorts (~100), making it difficult to determine the indications for TKA in this age group. Objectives We identified the number of patients &lt;21 years of age who underwent TKA in a US nationwide dataset. Additionally, we determined the epidemiological characteristics of patients undergoing TKA, including their age, sex, race, indications for surgery, and in-hospital mortality. Methods We analyzed the Kids’ Inpatient Database, which is a national weighted sample of all inpatient hospital admissions in the US in patients &lt;21 years old from ~4,200 hospitals in 46 states. We included all admissions from 2000-2016 with a primary procedural code of TKA determined by ICD-9 and 10 codes. Descriptive statistics such as means and percentages, along with 95% confidence intervals were calculated using appropriate sample weights. Results The total number of TKAs performed in patients &lt;21 years old from 2000 to 2016 was 1,331 (Table 1). The majority of TKAs performed (n=936; 70.3%) were for treatment of an oncologic disease. The most common diagnosis was malignant tumor (68.7%), followed by osteoarthritis (7.3%) and inflammatory arthritis or juvenile idiopathic arthritis (JIA) (7.0%) (Figure 1). Osteonecrosis accounted for 3.9% of cases, while mechanical complications accounted for 3.3%. Fewer than 2% of cases had an indication of either benign or uncertain tumor, infection, or trauma. The mean age was 14.8 years, and 48.4% of the cohort was female. A higher proportion of the non-tumor cohort was female (57.1%) than the tumor cohort (44.7%). 57.1% of patients in the overall cohort were White, and this proportion was smaller in the tumor group (53.8%) than the non-tumor group (64.9%). No patients died during the inpatient event. 87.8% of TKAs were performed in urban teaching hospitals. Table 1. Characteristics of patients &lt;21 undergoing TKA by diagnosis type Variable Overall N = 1331 Non-tumor N = 395 Tumor N = 936 Age, mean (95% CI) 14.8 (14.4, 15.2) 15.9 (14.7, 17.1) 14.3 (14.1, 14.6) Sex: Female, % (95% CI) 48.4 (44.9, 51.9) 57.1 (49.1, 64.8) 44.7 (41.1, 48.3) Race, % (95% CI) White 57.1 (52.3, 61.8) 64.9 (55.5, 73.3) 53.8 (48.4, 59.2) Black 13.1 (10.1, 16.9) 16.9 (10.1, 27.2) 11.5 (8.7, 14.9) Hispanic 19.7 (16.6, 23.3) 14.3 (9.9, 20.2) 22.0 (18.1, 26.6) Asian or Pacific Islander 3.4 (2.1, 5.4) ** 4.6 (2.9, 7.4) Native American 0.9 (0.4, 1.9) ** ** Other 5.8 (4.1, 8.1) 2.9 (1.3, 6.4) 7.0 (4.8, 10.0) Payor, % (95% CI) Medicare 1.4 (0.7, 2.9) 4.7 (2.2, 9.7) — Medicaid 31.1 (27.5, 35.0) 28.0 (21.0, 36.3) 32.4 (28.3, 36.7) Private 57.8 (53.7, 61.7) 60.2 (52.1, 67.8) 56.7 (52.2, 61.1) Self-pay 3.3 (2.3, 4.9) ** 4.2 (2.7, 6.2) Other 6.1 (4.4, 8.3) 5.1 (3.0, 8.6) 6.6 (4.5, 9.4) Admission type: elective, % (95% CI) 85.9 (81.1, 89.6) 81.6 (72.6, 88.2) 87.7 (82.2, 91.6) N represents weighted estimate CI = Confidence Interval ** Per HCUP guidelines, cell sizes ≤10 have been omitted to protect patient confidentiality Figure 1. Most common primary diagnoses for TKA in patients &lt;21 years old The most common primary diagnosis of 1,331 patients &lt;21 undergoing TKA. Bars represent 95% Confidence Intervals. JIA = juvenile idiopathic arthritis. Conclusion TKA is a rarely-performed procedure for patients &lt;21 years old in the US; it is mainly performed in urban teaching centers and has excellent in-hospital survival rates. 70.3% of these procedures are performed for tumors—the vast majority of which are malignant. Also, even with the advent of better treatment options for JIA and inflammatory arthritis, TKA is still performed frequently in this population indicating that better clinical management is needed. References [1]Martin JR et al. Adolescent total knee arthroplasty. PMCID: PMC5484984 Acknowledgements This work was supported by the Kellen Scholar Award supported by the Anna Marie and Stephen Kellen Foundation Total Knee Improvement Program. The authors would like to acknowledge the Healthcare Cost and Utilization Project Data Partners that contribute to Healthcare Cost and Utilization Project: Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, District of Columbia, Florida, Georgia, Hawaii, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming. Disclosure of Interests J. Alex Gibbons: None declared, Cynthia Kahlenberg: None declared, Deanna Jannat-Khah Shareholder of: AstraZeneca, Cytodyn, and Walgreens, Susan Goodman Consultant of: UCB, Grant/research support from: Novartis, Peter Sculco Consultant of: Intellijoint Surgical, DePuy Synthes, Lima Corporate, Zimmer Biomet, and EOS Imaging, Grant/research support from: Intellijoint Surgical and Zimmer Biomet, Mark Figgie Shareholder of: HS2, Mekanika, and Wishbone, Consultant of: Lima and Wishbone, Bella Mehta Paid instructor for: Novartis